A resistive random access memory (RRAM) device is a non-volatile memory device that stores data by varying the resistance of a resistive element. RRAM devices can have certain beneficial characteristics over other types of memory devices, such as low power consumption, high speed, and excellent bit resolution due to separation and a relatively large resistance ratio between a high resistance state (HRS) and a low resistance state (LRS), without the read/write cycle endurance limitations of charge-storage type memory.
The resistive element of an RRAM device has a current-voltage characteristic which may be varied in response to an applied voltage or current. Once the current-voltage characteristic is varied, the varied current-voltage characteristic of the resistive element may be maintained until a reset voltage or current is applied thereto. In some approaches, data may be written to a selected RRAM device by applying a predetermined voltage for a predetermined duration in a voltage-driven mode (VDM). Alternatively, data may be written by applying a predetermined current in a current-driven mode (CDM). As compared to VDM, CDM has a better on/off ratio, exhibits a relatively tight distribution of resistance, and achieves more complete dissolution of filament. When using the CDM to write an RRAM device, however, over-stress might occur in the RRAM device and cause damage thereto.
Like reference symbols in the various drawings indicate like elements.